How to carve a square using Ctrl+I?
select a loop of faces 
press I 
press again I 
scale by moving the mouse towards the center of your object 
Click  LMB  (left mouse button) 
press  E  do not move the mouse, I immediately 
press  S  and now scale to the desired size 
Click  LMB  (left mouse button) to end the action




NOTE


 I  (inset) x 1, with only one face selected, it will
create a single frame on that face
 I  (inset) x 1, with a loop of Selected faces will create a single frame on that face within the range of selected faces 
 I  (inset) x 2, with a single face selected will create a single frame within each face of the selected range